The present invention relates to vehicle bumper systems configured to reducing injury to pedestrians upon impact.
Modern bumper systems are designed to absorb a maximum of impact energy over a given stroke. At the same time, they are designed to minimize load spikes, and to distribute energy in a manner promoting uniform and predictable collapse upon undergoing a vehicle crash. Every millimeter of space is important to energy absorption, even spaces of 10 mm or less. Further, the individual components of an energy-absorbing system must combine well with other energy-absorbing components, e.g., metal tubular beams and non-tubular channels, injection-molded “honeycomb” energy absorbers, foam “block” energy absorbers, hydraulic shock absorbers, crush towers and mounts, and various combinations thereof. At the same time, light weight must be maintained. Also, it is desirable to maintain an ability to customize energy absorption at selected impact zones (e.g., at a corner of the vehicle or at a center impact, such as with a pedestrian impact). Concurrently, all components of a bumper system must be flexible and able to conform to an aerodynamic sweeping curvature of a vehicle front.
Notably, thermoformed parts have not been used much on exterior bumper systems for modern passenger vehicles, since energy absorbers are usually injection-molded to be relatively deep parts (such as about 40 mm or more deep) and include significant wall thickness (e.g., 3 mm or greater wall thickness) in order to provide a good crush stroke and energy absorption during impact. Further, most injection-molded energy absorbers made of solid polymer are relatively complex parts with undercut surfaces, varied wall thicknesses, and different wall spacings to provide optimal energy absorption in different regions of the energy absorbers. This is directly in opposition to thermoformed parts, which are traditionally limited to shorter depths, relatively thin wall thicknesses, and no undercut/blind surfaces. Thus, for years, original equipment manufacturers of passenger vehicles have avoided using thermoformed parts, despite the fact that thermoformed molds generally cost less, require shorter lead times, provide faster cycle times, have lower thermal energy use, generate less waste, and are more environmentally friendly processes. Skilled artisans in bumper design have apparently not fully realized the unexpected added benefits that thermoformed parts can offer when combined with other energy absorbing systems and components.
Thus, a system having the aforementioned advantages and solving the aforementioned problems is desired.